HSBC’s reputation was dragged through the dirt again today after it was accused of opening offshore accounts for drug dealers and serious criminals living the UK.

The conduct of Britain’s largest bank was thrown into the spotlight after tax authorities obtained details of more than 4,000 clients in Jersey. It comes less than a week after the bank said it had set aside $1.5 billion (£939 million) to cover fines for US regulatory breaches, including a failure to prevent Mexican drug money laundering.

The Jersey account holders are believed to include Daniel Bayes, a drug dealer now living in Venezuela, Michael Lee, who was convicted of possessing over 300 weapons at his house in Devon and three bankers facing fraud allegations and a man once nicknamed called London’s “number two computer crook”. HSBC is legally obliged to report any suspicions it has about money deposited in its accounts. It is not known whether the bank had already reported the accounts in question in question to HM Revenue and Customs.

In a statement, HSBC said: “We are investigating the reports of an alleged loss of certain client data in Jersey as a matter of urgency.

“We have not been notified of any investigation in relation to this matter by HMRC or any other authority but, should we receive notification, we will cooperate fully with the authorities.”

HMRC said it was “studying data” understood to have been sent by a whistle-blower.

“We value the information we receive from the public and business community,” it added.

“Clamping down on those who try to cheat the system through evading taxes and over claiming benefits is a top priority for us and we value the information we receive from the public and business community,” it added.